This invention relates to a brush head, particularly a toothbrush head, with a bristle carrier and bristles fixedly secured thereto, said bristle carrier having an elongated recess in which a multiplicity of bristles is received forming an elongated tuft with a closed, smooth outer contour corresponding essentially to the contour of the elongated recess.
This invention further relates to a method of manufacturing such a brush head, in which provision is made for a bristle carrier having a multiplicity of bristles fastened thereto.
Tufts can be fastened to bristle carriers of toothbrushes in various ways. A first method comprises arranging a tuft in a U-shaped configuration and, using a small metal anchor plate placed between the limbs of the U-shaped tuft, inserting it into a blind-end bore provided in the bristle carrier and fastening it there. The anchor plate lies over the U-shaped bend of the tuft and digs into opposing side walls of the blind-end bore. With this method referred to as anchor tufting it is mainly possible to fasten tufts of simple geometries, in particular those with a circular or square cross-section (cf. EP 0 700 259 B1).
A second method of fixedly securing the bristles to the bristle carrier comprises fastening the tufts by injection molding the material of the bristle carrier around the tufts (cf. EP 0 678 368 B1). With this method it is possible to fasten tufts of practically any cross-section and also any size to the bristle carrier.
A third method comprises the steps of inserting the tufts in a plastic perforated plate, welding together the bristle ends opposite the free end of the tufts by means of an embossing punch on the bottom side of the perforated plate, injection molding material onto the perforated plate with the tufts fastened thereto, and securing the perforated plate to a bristle carrier by adhesive bonding or alternatively, removably (cf. WO 99/55194). Tufts with variable cross-sectional geometries are obtainable with this embodiment, too, but the thermal welding of the bristles is, like the previously described injection molding operation, relatively complex and hence cost-intensive compared to the anchor tufting method.
A toothbrush head of the type initially referred to is known from U.S. Pat. No. 5,446,940, where the bristle carrier has several slot-type recesses, in each of which there is an elongated tuft with a closed, smooth outer contour. Because it is difficult to fill the slot-type recesses with bristles and align all the bristles in vertical direction it is proposed in U.S. Pat. No. 5,446,940 to replace the slot-type recess by several holes of circular or rectangular cross-section arranged in a row one behind the other and to fasten a separate tuft in each of these holes. The result, however, is not a single elongated tuft with a closed outer contour but a row of singular tufts arranged one behind the other. Furthermore, the size of the slot is limited by the anchor plates used.
The art also knows of an array of several circular tufts in a row one behind the other, in which the outer tufts can be inwardly inclined. To enable unhindered movement of the individual tufts it is proposed in said printed specification to space all the tufts a generous distance from one another. Mutual supporting of the individual tufts is to be prevented.
It is an object of the present invention to provide an improved brush head of the type initially referred to, as well as an improved method of the type initially referred to for its manufacture, which avoid the disadvantages known from the prior art and advance the prior art in advantageous manner. In particular it is intended to improve the manufacturability of a brush head having an elongated tuft of closed contour and to render the method of manufacturing more cost efficient.
This object is accomplished with a brush head of the type initially referred to in that, according to the invention, the elongated recess is divided by means of at least one transverse wall into several segments, a separate tuft is received in each of the segments, and the at least one transverse wall is constructed so that the separate tufts converge, forming in combination the elongated tuft with a closed, smooth outer contour.
Hence there are no completely separate individual tufts simply arranged in a row. At their fastening ends the tufts are separately joined and fastened, but at their free ends used to clean the teeth the bristles converge into a joint, elongated tuft and the division into separate tufts is no longer visible. This is important for the cleaning action and wear characteristics of the brushes.
To this effect the slot-type recess is constructed so that each segment has opposing side walls connected by the at least one transverse wall and extending symmetrically to the longitudinal axis of the slot-type recess, in particular parallel to each other. The side walls of contiguous segments lead continuously and steadily into each other and are interrupted solely by the transverse wall. The transverse walls lend stability to the bristle fixture to counter movement of the bristles in the longitudinal direction of the recess. They make it materially easier to fasten the bristles by the conventional anchor tufting method and, depending on the geometry of the recess, may even be a prerequisite for using this method.
In a further aspect of the invention the bristles of each separate tuft can be received in the respective segment in a U-shaped configuration and be held by a preferably plate-shaped anchor anchored in the respective segment. The anchor can extend between the limbs of the U-bent bristles over their connecting sections, holding them against the bottom of the slot-shaped recess. Hence there is no need for the bristles to be fixed in place by injection molding, adhesive bonding or welding. They can be anchored with a separate anchor to the bristle carrier by positive and frictional engagement. A brush head of such construction is far less costly to manufacture than conventional brush heads with elongated tufts.
The anchors provided in the individual segments to anchor the tufts can be arranged in various ways. According to a preferred embodiment of the invention the anchors extend in a direction essentially transverse to the longitudinal axis of the slot-type recess, meaning essentially or nearly parallel to the respectively neighboring transverse wall of the respective segment. The anchor preferably forms an angle of less than 30 degrees with the respectively neighboring transverse wall. The longitudinal axis of the slot-type recess is not necessarily straight in the context of the present invention, but rather the longitudinal alignment of the slot-type recess can be adapted to the conditions of the respective brush head, in particular can be curved or kinked, so that an angle can be formed between the anchor and the respectively neighboring transverse wall of the respective segment. Thanks to the alignment of the anchors in a direction essentially transverse to the longitudinal axis of the slot-type recess, the tufts in the respective segment are able to adapt to its contour to the best possible effect. The tufts anchored in the individual segments form, in particularly advantageous manner, the desired closed contour of the elongated tuft.
The at least one transverse wall in the slot-type recess can be constructed in various ways and forms. A preferred embodiment of the invention consists of providing a separately constructed transverse bar anchored to the bristle carrier to serve as the transverse wall. Provision can be made preferably for a thin metal bar which is anchored in opposing side walls of the slot-type recess. In particular it is possible to shoot an anchor wire or an anchor plate, of the type normally used to fasten the bristles, into the slot-type recess to serve as the transverse wall. However, to serve as the transverse wall the anchor plate or a comparable plate is inserted in advance without bristles in the slot-type recess so that the respective tuft can subsequently be inserted in the already existing segment. The height of the transverse walls from the bottom of the slot type recess can differ from the height of the anchors used to anchor the tufts.
To keep the distance between the individual tufts as small as possible at their fastened ends already, the thickness of the at least one transverse wall is preferably less than 0.5 mm, particularly 0.3 mm or less. According to a preferred embodiment of the invention the transverse wall has a thickness in the region of around 0.15 to 0.3 mm. With this thickness it is possible to obtain an elongated tuft of high density and compactness. In spite of the small thickness of the metal transverse wall the latter offers sufficient stability for anchoring the tufts in the segments using the anchor tufting method.
To prevent the bristles from tearing or kinking during tufting into the segments, the transverse wall is constructed without sharp edges. In particular the upper edge of the transverse wall close to the outside of the slot-type recess is rounded off. It is also possible for the transverse wall on the whole to have an oval or elliptical cross-section.
According to a further embodiment of the invention the at least one transverse wall is made in one integral piece with the bristle carrier. Preferably it is made together with the bristle carrier of an injected-molded plastics material and is molded thereto. For the tufts of the separate segments to converge in a joint tuft in spite of correspondingly greater thickness of the plastic transverse wall, which at like thickness displays less stability than the previously mentioned metal transverse wall, opposing sides of the at least one transverse wall are inclined toward each other so that the tufts sitting in neighboring segments have their free ends inclined toward each other. Hence in this embodiment, too, the tufts form at least in their regions close to the free ends of the bristles a joint and on the whole elongated tuft with a closed, smooth outer contour, creating the impression that a single elongated tuft is fastened in the slot-type mount.
The at least one transverse wall is constructed particularly in the shape of a wedge. Its cross-section tapers from the bottom of the slot-type recess to the outside. It is possible for a single side of the transverse wall to be inclined to the perpendicular drawn upon the top of the bristle carrier. It is also possible, however, for both sides of the transverse wall to be correspondingly inclined or, if there are various transverse walls, for there to be combinations of the above mentioned solutions.
In a further aspect of the invention it is possible for outer lying segments of the slot-type recess to be on the whole inwardly inclined toward a central segment. Hence with this embodiment it is not only inner walls of the outer segments, meaning the respective sides of the corresponding transverse wall, but also the end walls of the slot-type recess and, where applicable, the bottom of the slot-type recess in this segment which are inclined so that the tufts accommodated therein lean toward the central tuft. This prevents the tufts fastened in the outer segments from fanning out, resulting in a higher density also in this area. In an advantageous further development the tufts of the individual segments are inclined at different angles or directions with respect to the perpendicular drawn upon the top. In this configuration the area of the brush disk is put to optimal use compared to conventional tufting arrays with separate holes where the number of tufts is significantly lower.
With a view to ease of manufacturability, however, the previously described version with only inclined sides of the transverse wall is to be preferred because it facilitates the shaping of suitable injection molds.
In a further aspect of the invention the segments can have essentially the same base area so that the on the whole elongated tuft takes on a uniform density and structure.
To obtain a cascade-type bristle array within an elongated tuft it is possible for the segments to have different base areas. A different number of bristles can be accommodated in each of the different segments. It is also possible for different types of bristles to be received in the different segments. Bristles of different length, structure, material, stiffness, diameter or color can be used.
The segments can have different types of contour. In particular they have a non-circular contour, preferably an angular contour with at least two essentially parallel opposing sides. The segments can also have an elliptical or oval shape, if required.
In a method of manufacturing a brush head of the type initially referred to, the previously mentioned object of the present invention is accomplished by providing in the bristle carrier a slot-type recess having at least one transverse wall dividing the recess into several segments, and inserting in each segment a separate tuft, wherein the at least one transverse wall is constructed in such a way that the separate tufts converge, forming in combination an elongated tuft with a closed, smooth outer contour.
In particular the bristles are inserted in the individual segments of the slot-type recess by the anchor tufting method. The bristles of each tuft are laid in a U-shaped configuration around a metal anchor and in this U-shape are shot with the metal anchor into the respective segment. In the process the anchor is driven into the side walls of the slot-type recess and becomes anchored therein. With the anchor tufting method it is possible to anchor the bristles cheaply and at high speed to the bristle carrier. In conjunction with the division of the slot-type recess it is possible to provide an elongated tuft on the brush head in a low-cost and time-efficient manner.
According to a preferred embodiment of the invention the slot-type recess is initially constructed without a transverse wall. A separate transverse wall is subsequently inserted, anchored in particular to opposing side walls of the recess. The advantage of subsequently inserting the transverse wall or the transverse walls is that different materials can be used for the bristle carrier and the transverse wall, thus enabling the most suitable material to be chosen for the bristle carrier and the transverse wall independently of each other. In particular it is possible for a metal plate to be shot in a direction essentially transverse to the longitudinal axis of the slot-type recess into opposing side walls of the recess to serve as the transverse wall. It is particularly advantageous to anchor a metal anchor, of the type conventionally used to fasten the bristles in the anchor tufting method, as the transverse wall in advance, meaning before inserting the bristles in the slot-type recess.
According to another preferred embodiment of the invention the at least one transverse wall is integrally molded on the bristle carrier. In particular it can be injection-molded of a plastics material together with the bristle carrier. If necessary, the bristle carrier can be shaped after the injection molding operation as by drilling, milling and similar operations in order to lend the transverse wall the desired shape.
In the two described ways of constructing the transverse wall the tufts are inserted in the respective segment in a subsequent process step after the transverse wall is constructed. In a further aspect of the invention the tufts can be inserted in an approximately circular configuration in the respective segment. In the process the tufts automatically adapt to the respective contour of the segment, meaning they change their initially roughly circular cross-sectional shape into the cross-sectional shape corresponding to the respective segment. In particular it is possible to use a conventional tuft inserting machine which can be set up for round tufts. This simplifies the manufacturing process inasmuch as it is possible to use equipment that is already available. Fastening the tufts can be performed at maximum speed; up to 850 tufts per minute are possible, for example.
Bristles which indicate their state of wear, for example by changing color, can be used to advantage. Such bristles are not available as a rule on reels and so cannot be used at all or only with additional expense when fastened by injection molding or welding techniques.
The elongated clusters or tufts of bristles can be advantageously arranged in the outer area of the toothbrush in such a way that the envelope extends essentially parallel to the contour of the bristle carrier. The wear characteristics and fanning of the tufts are greatly reduced, particularly on oscillating/rotating toothbrushes. Furthermore, the removal of plaque from the gingival region can be improved.
Further features, application possibilities and advantages of the present invention will become apparent from the subsequent description of embodiments of the invention illustrated in the Figures of the accompanying drawings. It will be understood that any feature described or represented by illustration, whether used singularly or in combination, forms the subject-matter of the present invention, irrespective of their summary in the patent claims or their back reference and irrespective of their wording and representation in the description and the drawings, respectively.
The present invention will be described in more detail in the following with reference to preferred embodiments and associated drawings.